U.S. patent application number 16/636750 was filed with the patent office on 2020-07-09 for silicon carbide epitaxial substrate.
The applicant listed for this patent is SUMITOMO ELECTRIC INDUSTRIES, LTD.. Invention is credited to Tsutomu HORI, Takaya MIYASE.
Application Number | 20200219981 16/636750 |
Document ID | / |
Family ID | 65439455 |
Filed Date | 2020-07-09 |
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United States Patent
Application |
20200219981 |
Kind Code |
A1 |
HORI; Tsutomu ; et
al. |
July 9, 2020 |
SILICON CARBIDE EPITAXIAL SUBSTRATE
Abstract
A silicon carbide epitaxial substrate includes: a silicon
carbide single-crystal substrate having a polytype of 4H and having
a principal surface inclined at an angle .theta. from a {0001}
plane in a <11-20> direction; and a silicon carbide epitaxial
layer provided on the principal surface and having a basal plane
dislocation, wherein even when the basal plane dislocation is
irradiated with an ultraviolet light having a power of 270 mW and a
wavelength of 313 nm for 10 seconds, the basal plane dislocation
does not move.
Inventors: |
HORI; Tsutomu; (Osaka,
JP) ; MIYASE; Takaya; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO ELECTRIC INDUSTRIES, LTD. |
Osaka |
|
JP |
|
|
Family ID: |
65439455 |
Appl. No.: |
16/636750 |
Filed: |
April 26, 2018 |
PCT Filed: |
April 26, 2018 |
PCT NO: |
PCT/JP2018/017038 |
371 Date: |
February 5, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C30B 29/36 20130101;
H01L 29/045 20130101; H01L 29/161 20130101; H01L 29/1608
20130101 |
International
Class: |
H01L 29/16 20060101
H01L029/16; H01L 29/04 20060101 H01L029/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2017 |
JP |
2017-161249 |
Claims
1. A silicon carbide epitaxial substrate comprising: a silicon
carbide single-crystal substrate having a polytype of 4H and having
a principal surface inclined at an angle .theta. from a {0001}
plane in a <11-20> direction; and a silicon carbide epitaxial
layer provided on the principal surface and having a basal plane
dislocation, wherein even when the basal plane dislocation is
irradiated with an ultraviolet light having a power of 270 mW and a
wavelength of 313 nm for 10 seconds, the basal plane dislocation
does not move.
2. The silicon carbide epitaxial substrate according to claim 1,
wherein a diameter of the silicon carbide single-crystal substrate
is greater than or equal to 150 mm.
3. The silicon carbide epitaxial substrate according to claim 1,
wherein the angle .theta. is greater than 0.degree. and less than
or equal to 6.degree..
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a silicon carbide
epitaxial substrate.
[0002] The present application is based on and claims priority to
Japanese Patent Application No. 2017-161249, filed on Aug. 24,
2017, the entire contents of the Japanese Patent Application are
hereby incorporated herein by reference.
BACKGROUND ART
[0003] For a method of manufacturing a semiconductor device using a
silicon carbide epitaxial substrate, a manufacturing method by
which the yield rate can be enhanced is disclosed (for example,
Patent Document 1).
PRIOR ART DOCUMENT
Patent Document
[0004] [Patent Document 1] Japanese Laid-open Patent Publication
No. 2013-112575
SUMMARY OF THE INVENTION
[0005] According to one aspect of the present embodiment, a silicon
carbide epitaxial substrate includes: a silicon carbide
single-crystal substrate having a polytype of 4H and having a
principal surface inclined at an angle .theta. from a {0001} plane
in a <11-20> direction; and a silicon carbide epitaxial layer
provided on the principal surface and having a basal plane
dislocation. Even when the basal plane dislocation is irradiated
with an ultraviolet light having a power of 270 mW and a wavelength
of 313 nm for 10 seconds, the basal plane dislocation does not
move.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a partial cross-sectional view schematically
illustrating a silicon carbide epitaxial substrate according to one
aspect of the present disclosure;
[0007] FIG. 2A is an explanatory diagram (1) of a basal plane
dislocation whose position is moved by irradiation with an
ultraviolet light;
[0008] FIG. 2B is an explanatory diagram (2) of the basal plane
dislocation whose position is moved by irradiation with an
ultraviolet light;
[0009] FIG. 3 is a top view schematically illustrating the silicon
carbide epitaxial substrate according to one aspect of the present
disclosure;
[0010] FIG. 4 is a cross-sectional view schematically illustrating
an example of a configuration of a film deposition apparatus;
[0011] FIG. 5 is a schematic top view illustrating the inside of a
chamber of the film deposition apparatus;
[0012] FIG. 6 is a flowchart schematically illustrating a method
for manufacturing the silicon carbide epitaxial substrate according
to one aspect of the present disclosure;
[0013] FIG. 7A is a process diagram (1) schematically illustrating
the method for manufacturing the silicon carbide semiconductor
device according to one aspect of the present disclosure;
[0014] FIG. 7B is a process diagram (2) schematically illustrating
the method for manufacturing the silicon carbide semiconductor
device according to one aspect of the present disclosure;
[0015] FIG. 7C is a process diagram (3) schematically illustrating
the method for manufacturing the silicon carbide semiconductor
device according to one aspect of the present disclosure; and
[0016] FIG. 8 is a timing chart illustrating an example of
temperature control and gas flow rate control in the film
deposition apparatus.
EMBODIMENT FOR CARRYING OUT THE INVENTION
[0017] The present disclosure has an object to provide a silicon
carbide epitaxial substrate in which a basal plane dislocation does
not move even when being irradiated with an ultraviolet light.
[0018] According to the present disclosure, it is possible to
provide a silicon carbide epitaxial substrate in which a basal
plane dislocation does not move even when being irradiated with an
ultraviolet light.
[0019] In the following, an embodiment to be carried out will be
described. Note that the same reference characters are allotted to
the same members and the like so that their descriptions are
omitted.
Description of Embodiment of the Present Disclosure
[0020] To begin with, aspects of the present disclosure are listed
and described below. In the following description, the same
reference characters are allotted to the same or corresponding
elements and the same descriptions thereof are not repeated. In
addition, regarding crystallographic denotation herein, an
individual orientation, a group orientation, an individual plane,
and a group plane are indicated by [ ], < >, ( ), and { },
respectively. Here, although a crystallographically negative index
is usually expressed by a number with a bar "-" thereabove, a
negative sign herein precedes a number to express a
crystallographically negative index in this specification. In
addition, the epitaxial growth of the present disclosure is a
homoepitaxial growth.
[0021] [1] A silicon carbide epitaxial substrate according to one
aspect of the present disclosure includes: a silicon carbide
single-crystal substrate having a polytype of 4H and having a
principal surface inclined at an angle .theta. from a {0001} plane
in a <11-20> direction; and a silicon carbide epitaxial layer
provided on the principal surface and having a basal plane
dislocation, wherein even when the basal plane dislocation is
irradiated with an ultraviolet light having a power of 270 mW and a
wavelength of 313 nm for 10 seconds, the basal plane dislocation
does not move.
[0022] As a result of research, the inventors of the present
application have found, in a silicon carbide epitaxial substrate in
which a silicon carbide epitaxial layer is famed on a silicon
carbide single-crystal substrate, a basal plane dislocation that
moves on the surface of the silicon carbide epitaxial layer upon
being irradiated with an ultraviolet light having a wavelength of
313 nm. In a case where a semiconductor device is manufactured by
using a silicon carbide epitaxial substrate in which such a basal
plane dislocation is present, there may be a possibility that the
basal plane dislocation moves during a proves of manufacturing the
semiconductor device, which may decrease the reliability of the
semiconductor device to be manufactured.
[0023] Furthermore, the inventors of the present application have
continued research and found that, upon irradiation with an
ultraviolet light having a predetermined power for a predetermined
time or longer, the movement of a basal plane dislocation moving on
the surface of the silicon carbide epitaxial layer is stopped, and
the position of the basal plane dislocation is stabilized. In such
a silicon carbide epitaxial substrate in which the position of the
basal plane dislocation is stabilized, even when the surface of the
silicon carbide epitaxial layer is further irradiated with an
ultraviolet light having a power of 270 mW and a wavelength of 313
nm for 10 seconds, the basal plane dislocation does not move.
Therefore, by using such a silicon carbide epitaxial substrate to
manufacture a semiconductor device, the reliability of the
semiconductor device can be enhanced.
[0024] [2] A diameter of the silicon carbide single-crystal
substrate is greater than or equal to 150 mm.
[0025] [3] The angle .theta. is greater than 0.degree. and less
than or equal to 6.degree..
Details of Embodiment of the Present Disclosure
[0026] In the following, an embodiment of the present disclosure
(which is hereinafter referred to as the "present embodiment") will
be described in detail, but the present embodiment is not limited
to the following.
[0027] [Silicon Carbide Epitaxial Substrate]
[0028] In the following, a silicon carbide epitaxial substrate 100
according to the present embodiment will be described.
[0029] FIG. 1 is a cross-sectional view illustrating an example of
a structure of the silicon carbide epitaxial substrate 100
according to the present embodiment. The silicon carbide epitaxial
substrate 100 according to the present embodiment includes a
silicon carbide single-crystal substrate 10 having a principal
surface 10A inclined at an off angle .theta. from a predetermined
crystal plane, and a silicon carbide epitaxial layer 11 formed on
the principal surface 10A of the silicon carbide single-crystal
substrate 10. The predetermined crystal plane is preferably a
(0001) plane or a (000-1) plane.
[0030] Note that a polytype of silicon carbide in the silicon
carbide single-crystal substrate 10 is a 4H. This is because the 4H
polytype silicon carbide excels the other polytypes in electron
mobility, dielectric breakdown strength, and the like. The diameter
of the silicon carbide single-crystal substrate 10 is greater than
or equal to 150 mm (e.g., greater than or equal to 6 inches). This
is because increasing the diameter has an advantage in reducing the
cost of manufacturing a semiconductor device. In the silicon
carbide single-crystal substrate 10, the principal surface 10A is
inclined with respect to the {0001} plane at an off angle .theta.
of 4.degree. in the <11-20> direction. Note that according to
the present embodiment, the off angle .theta. may exceed 0.degree.
and may be 6.degree. or less.
[0031] In the silicon carbide epitaxial substrate 100 according to
the present embodiment, even when the surface 100A of the silicon
carbide epitaxial substrate 100 is irradiated with an ultraviolet
light having a power of 270 mW and a wavelength of 313 nm for 10
seconds, the basal plane dislocation does not move. Note that
according to the present embodiment, a surface 11A of a silicon
carbide epitaxial layer 11 becomes the surface 100A of the silicon
carbide epitaxial substrate 100.
[0032] [Basal Plane Dislocation]
[0033] Next, a basal plane dislocation of the silicon carbide
epitaxial substrate 100 according to the present embodiment will be
described. As described above, as a result of researching silicon
carbide epitaxial substrates, the inventors of the present
application have found that, among basal plane dislocations that
are present in silicon carbide epitaxial substrates, a basal plane
dislocation is present that moves upon being irradiated with an
ultraviolet light. Specifically, upon the surface of the silicon
carbide epitaxial layer 11 of the silicon carbide epitaxial
substrate 100 being irradiated with an ultraviolet light having a
wavelength of 313 nm, a basal plane dislocation 110 presenting at
the position illustrated in FIG. 2A moves in the direction
indicated by the dashed arrow in FIG. 2B. Although the basal plane
dislocation 110 illustrated in FIGS. 2A and 2B is a basal plane
dislocation that long extends in the <1-100> direction, it
was confirmed that, upon being irradiated with an ultraviolet light
having a wavelength of 313 nm, the basal plane dislocation 110
parallel moves in the <11-20> direction, maintaining a state
of extending in the <1-100> direction. Thus, when a basal
plane dislocation in a silicon carbide epitaxial substrate is moved
by irradiation with an ultraviolet light, at the time of
manufacturing a semiconductor device, the basal plane dislocation
may move to an area where the semiconductor device is formed,
resulting in a decrease in the characteristics and a decrease in
the yield rate of the semiconductor device to be manufactured. At
the time of manufacturing a semiconductor device, a process in
which a basal plane dislocation possibly moves may be a process
such as a lithography process in which an exposure device performs
irradiation with an ultraviolet light or the like or a process of
deposition or substrate processing by plasma in which an
ultraviolet light is radiated.
[0034] Furthermore, as a result of researching silicon carbide
epitaxial substrates, the inventors of the present application have
found that, upon irradiation with an ultraviolet light having a
predetermined power for a predetermined time or longer, the
movement of a basal plane dislocation is stopped. Specifically, the
inventors of the present application have found that, upon
irradiation with an ultraviolet light having a wavelength of 313 nm
at an irradiation intensity of 270 mW for 10 seconds, the position
of a basal plane dislocation does not move even when being
irradiated with an ultraviolet light after that. The silicon
carbide epitaxial substrate 100 according to the present embodiment
is based on the findings obtained as described above. That is, the
silicon carbide epitaxial substrate 100 is manufactured, after
depositing the silicon carbide epitaxial layer 11, by being
irradiated with an ultraviolet light having a wavelength of 313 nm
at an irradiation intensity of 270 mW for 10 seconds.
[0035] In the silicon carbide epitaxial substrate 100 according to
the present embodiment, because the movement of the basal plane
dislocation due to irradiation with an ultraviolet light is
stopped, the basal plane dislocation does not move even when
further being irradiated with an ultraviolet light having a
wavelength of 313 nm at an irradiation intensity of 270 mW for 10
seconds.
[0036] According to the present embodiment, the measurement of
whether or not the basal plane dislocation moves is determined by
performing the measurement at four measurement areas 101a, 101b,
101c, and 101d of the peripheral portion on the surface of the
silicon carbide epitaxial substrate 100 illustrated in FIG. 3. For
silicon carbide epitaxial substrates, dislocations such as a basal
plane dislocation are more likely to be seen at a peripheral
portion than a central portion. Also, for silicon carbide epitaxial
substrates with many dislocations such as a basal plane dislocation
at a central portion, dislocations such as a basal plane
dislocation at a peripheral portion tend to be seen often.
[0037] Specifically, the measurement areas 101a, 101b, 101c, and
101d are provided at 45.degree., 135.degree., 225.degree., and
315.degree. in the clockwise direction, with reference to the
direction from a center 100a of the silicon carbide epitaxial
substrate 100 toward a center OFC of an orientation flat OF. The
measurement areas 101a, 101b, 101c, and 101d are square areas of
2.6 mm*2.6 mm in size, and are provided at positions approximately
1 mm away from an edge 100b around the silicon carbide epitaxial
substrate 100.
[0038] According to the present embodiment, using a mercury xenon
lamp mounted on PLI-200 (manufactured by Photon Design
Corporation), the silicon carbide epitaxial substrate 100 is
irradiated for 10 seconds with an ultraviolet light transmitted
through a 313 nm bandpass filter. Note that the power of the
ultraviolet light transmitted through the bandpass filter is 270
mW. According to the silicon carbide epitaxial substrate 100
according to the present embodiment, at the measurement areas 101a,
101b, 101c, and 101d, even when being irradiated with the above
described ultraviolet light, the basal plane dislocation does not
move from the position before being irradiated.
[0039] [Film Deposition Apparatus]
[0040] Next, a method for manufacturing a silicon carbide epitaxial
substrate according to the present embodiment will be described. To
begin with, a film deposition apparatus for manufacturing a silicon
carbide epitaxial substrate according to the present embodiment
will be described with reference to FIG. 4 and FIG. 5. FIG. 4 is a
schematic cross-sectional view illustrating an example of a
configuration of the film deposition apparatus that is used in the
present embodiment. FIG. 5 is a top view of the inside of a chamber
of the film deposition apparatus as viewed from above. The film
deposition apparatus 400 illustrated in FIG. 4 and FIG. 5 is a
horizontal hot wall CVD (Chemical Vapor Deposition) apparatus. As
illustrated in FIG. 4, the film deposition apparatus 400 includes
induction heating coils 403, a quartz tube 404, a heat insulator
405, and a heating element 406. The heating element 406 is, for
example, made of carbon. The heating element 406 is integrally
formed so as to have a rectangular tube shape, and inside the
rectangular heating element 406, two flat portions are formed so as
to face each other. A space surrounded by the two flat portions is
a chamber 401. The chamber 401 is also referred to as a "gas flow
channel". As illustrated in FIG. 5, on a rotatable susceptor 408 in
the chamber 401, a substrate holder 407 on which a plurality of,
for example, three, silicon carbide single-crystal substrates 10
can be placed is installed.
[0041] The heat insulator 405 is arranged so as to surround the
outer circumferential portion of the heating element 406. The
chamber 401 is thermally insulated from the outside of the film
deposition apparatus 400 by the heat insulator 405. The quartz tube
404 is arranged so as to surround the outer circumferential portion
of the heat insulator 405. The induction heating coils 403 are
wound around the outer circumferential portion of the quartz tube
404. In the film deposition apparatus 400, the heating element 406
is inductively heated by supplying an alternate current to the
induction heating coils 403, and a temperature in the chamber 401
can be controlled. At this time, due to heat insulation by the heat
insulator 405, the quartz tube 404 is hardly heated.
[0042] In the film deposition apparatus 400 illustrated in FIG. 4,
the chamber 401 is evacuated in the direction indicated by the
dashed arrow A. Also, at the time of depositing the silicon carbide
epitaxial layer 11, a gas containing a carbon component as a
material gas, a gas containing a silicon component, hydrogen
(H.sub.2) gas as a carrier gas, and, as needed, a gas containing a
nitrogen component are supplied from the direction indicated by the
dashed arrow B. According to the present embodiment, propane
(C.sub.3H.sub.3) gas or the like is used as the gas containing a
carbon component, and silane (SiH.sub.4) gas or the like is used as
the gas containing a silicon component.
[0043] At the time of depositing the silicon carbide epitaxial
layer 11, the rotatable susceptor 408 is rotated in the direction
indicated by the dashed arrow C about a rotation axis 407A of the
substrate holder 407. Thereby, the silicon carbide single-crystal
substrate 10 placed on the substrate holder 407 can be revolved.
Note that according to the present embodiment, the substrate holder
407 is rotated by rotating the rotatable susceptor 408 about a
perpendicular direction, as an axis, with respect to the principal
surface 10A of the silicon carbide single-crystal substrate 10. The
rotation speed of the rotatable susceptor 408 can be, for example,
greater than or equal to 10 RPM and less than or equal to 100 RPM.
Accordingly, in the deposition device 400, silicon carbide
epitaxial layers 11 can be deposited simultaneously on, a plurality
of, for example, three silicon carbide single-crystal substrates
10. Note that the substrate holder 407 is rotated by, for example,
a gas flow method.
[0044] [Method for Manufacturing Silicon Carbide Epitaxial
Substrate]
[0045] Next, a method for manufacturing a silicon carbide epitaxial
substrate according to the present embodiment will be described.
The method for manufacturing the silicon carbide epitaxial
substrate according to the present embodiment will be described
with reference to FIG. 6.
[0046] First, a preparation process (S102) is performed to prepare
a silicon carbide single-crystal substrate 10. The silicon carbide
single-crystal substrate 10 is produced by slicing an ingot of a
silicon carbide single crystal. For example, a wire saw is used to
slice the ingot of the silicon carbide single crystal. FIG. 7A
schematically illustrates the silicon carbide single-crystal
substrate 10 sliced in this manner.
[0047] The silicon carbide single-crystal substrate 10 includes a
principal surface 10A on which a silicon carbide epitaxial layer 11
is to be grown later. The silicon carbide single-crystal substrate
10 has an off angle 9 that is greater than 0.degree. and less than
or equal to 6.degree.. In other words, the principal surface 10A is
a surface inclined by an off angle .theta. that is greater than
0.degree. and less than or equal to 6.degree. from a predetermined
crystal plane. By introducing the off angle .theta. into the
silicon carbide single-crystal substrate 10, when the silicon
carbide epitaxial layer 11 is grown by a CVD method, a lateral
growth from an atomic step that appears on the principal surface
10A, a called "step flow growth," is induced. Thus, a single
crystal grows while inheriting a polytype of the silicon carbide
single-crystal substrate 10, thereby inhibiting a different type of
polytype from being mixed. Here, the predetermined crystal plane is
preferably a (0001) plane or a (000-1) plane. In other words, the
predetermined crystal plane is preferably a {0001} plane. A
direction in which an off angle is provided is a <11-20>
direction.
[0048] Next, a decompression process (S104) is performed. In the
decompression process (S104), as illustrated in FIG. 4 and FIG. 5,
the silicon carbide single-crystal substrate 10 is placed in the
chamber 401 of the film deposition apparatus 400, and the pressure
in the chamber 401 is decreased. The silicon carbide single-crystal
substrate 10 is placed on the rotatable susceptor 408 in the
chamber 401. The rotatable susceptor 408 may be coated with a SiC
coating or the like.
[0049] FIG. 8 is a timing chart illustrating a temperature and a
gas flow rate in the chamber 401 from the decompression process
(S104) to the cooling process (S110). In FIG. 8, the decompression
process (S104) corresponds to a period from time t1 when the
decompression of the chamber 401 starts after the silicon carbide
single-crystal substrate 10 is placed in the chamber 401 to time t2
when the pressure in the chamber 401 reaches a targeted value. The
targeted value of the pressure in the decompression process (S104)
is, for example, about 1*10.sup.-6 Pa.
[0050] Next, a temperature rising process (S106) is performed. In
the temperature rising process (S106), the temperature in the
chamber 401 of the film deposition apparatus 400 is heated to a
second temperature T2. In the temperature rising process (S106),
after the temperature passes a first temperature T1 that is lower
than the second temperature T2, the temperature reaches the second
temperature T2. As illustrated in FIG. 8, the temperature rising
starts from time t2; the temperature in the chamber 401 reaches the
first temperature T1 at time t3; and the temperature in the chamber
401 further reaches the second temperature T2 at time t4.
[0051] The first temperature T1 is, for example, 1100.degree. C.
Also, the second temperature T2 is preferably greater than or equal
to 1500.degree. C. and less than or equal to 1700.degree. C. When
the second temperature T2 is below 1500.degree. C., it may be
difficult to uniformly grow a single crystal in an epitaxial growth
process (S108) that will be described later, and the growth rate
may decrease. Also, when the second temperature T2 is greater than
1700.degree. C., an etching action by hydrogen gas becomes intense,
and the growth rate may decrease. The second temperature T2 is more
preferably greater than or equal to 1520.degree. C. and less than
or equal to 1680.degree. C., and is particularly preferably greater
than or equal to 1550.degree. C. and less than or equal to
1650.degree. C. According to the present embodiment, the second
temperature T2 is 1630.degree. C.
[0052] According to the present embodiment, as illustrated in FIG.
8, from time t3 when the temperature in the chamber 401 reaches the
first temperature T1, hydrogen (H.sub.2) gas is supplied into the
chamber 401 and the pressure in the chamber 401 is set to be a
predetermined pressure, for example, 8 kPa. The hydrogen gas is
supplied such that the flow rate of the hydrogen gas becomes 120
slm.
[0053] Next, an epitaxial growth process (S108) is performed. In
the epitaxial growth process (S108), together with the hydrogen
gas, a hydrocarbon gas and silane (SiH.sub.4) gas are supplied into
the chamber 401 of the film deposition apparatus 400. The
predetermined pressure in the chamber 401 in the epitaxial growth
process (S108) is, for example, 8 kPa. Thus, the silicon carbide
epitaxial layer 11 can be grown on the principal surface 10A of the
silicon carbide single-crystal substrate 10.
[0054] Methane (CH.sub.4) gas, ethane (C.sub.2H.sub.6) gas, propane
(C.sub.3H.sub.8) gas, butane (C.sub.4H.sub.10) gas, acetylene
(C.sub.2H.sub.2) gas, and the like can be used as the hydrocarbon
gas. Among these hydrocarbon gases, a single kind of gas may be
used alone, or two or more kinds may be mixed to be used. In other
words, the hydrocarbon gas preferably contains one or more kinds
selected from the group consisting of methane gas, ethane gas,
propane gas, butane gas and acetylene gas. A flow rate of the
hydrocarbon gas is preferably greater than or equal to 5 sccm and
less than or equal to 30 sccm. According to the present embodiment,
for example, propane gas is supplied as the hydrocarbon gas at 15
sccm.
[0055] Moreover, the flow rate of the silane gas is not
specifically limited, but the flow rate of the silane gas is
preferably adjusted such that a ratio (C/Si) of a number of carbon
(C) atoms contained in the hydrocarbon gas to a number of silicon
(Si) atoms contained in the silane gas becomes 0.5 or more and 2.0
or less. This is for an epitaxial growth of SiC having an
appropriate stoichiometric ratio. According to the present
embodiment, for example, the silane gas is supplied at 45 sccm.
[0056] In the epitaxial growth process (S108), nitrogen (N.sub.2)
and the like may be supplied as a dopant. The epitaxial growth
process (S108) is started at time t4 to time t5 in accordance with
a targeted thickness of the silicon carbide epitaxial layer 11.
FIG. 7B schematically illustrates a silicon carbide epitaxial
substrate in which the silicon carbide epitaxial layer 11 is
deposited on the principal surface 10A of the silicon carbide
single-crystal substrate 10.
[0057] Next, a cooling process (S110) is performed. In the cooling
process (S110), heating is stopped at time t5 when the epitaxial
growth process (S108) is completed, and cooling is performed while
the flow rate of hydrogen gas is supplied. At that time, the
predetermined pressure in the chamber 401 is, for example, 8 kPa.
Thereafter, the supply of the hydrogen gas is stopped at time t6
when the temperature T3 becomes 600.degree. C., and cooling is
performed until time t7 when the silicon carbide epitaxial
substrate becomes able to be taken out at the temperature. After
reaching time t7, the inside of the chamber 401 is opened to
atmosphere, the inside of the chamber 401 is returned to
atmospheric pressure, and the silicon carbide epitaxial substrate
is removed from the inside of the chamber 401.
[0058] Next, a basal plane dislocation stabilization process (S112)
is performed. In the basal plane dislocation stabilization process
S112, the surface of the silicon carbide epitaxial layer 11 of the
silicon carbide epitaxial substrate on which the silicon carbide
epitaxial layer 11 is deposited is irradiated with an ultraviolet
light. Specifically, using a mercury xenon lamp, the surface of the
silicon carbide epitaxial layer 11 is irradiated with an
ultraviolet light transmitted through a 313 nm bandpass filter and
having an intensity of 270 mW for 10 seconds. Thereby, the basal
plane dislocation, which moves by irradiation with an ultraviolet
light, no longer moves and the position of the basal plane
dislocation is stabilized. FIG. 7C schematically illustrates a
state in which the surface is irradiated with an ultraviolet light
where the silicon carbide epitaxial layer 11 of the silicon carbide
epitaxial substrate is deposited.
[0059] Through the above processes, the silicon carbide epitaxial
substrate according to the present embodiment can be
manufactured.
[0060] Note that although a case has been described above in which
the basal plane dislocation, which moves by irradiation with an
ultraviolet light, is stabilized by irradiation with an ultraviolet
light, if it is possible to stabilize the position of the basal
plane dislocation, irradiation may be performed with light having
another wavelength or electromagnetic waves or the like.
[0061] Although the embodiment has been described above in detail,
it is not limited to a specific embodiment, and various
modifications and changes can be made within the scope described in
claims.
DESCRIPTION OF THE REFERENCE NUMERALS
[0062] 10 silicon carbide single-crystal substrate [0063] 10A
principal surface [0064] 10B back surface [0065] 11 silicon carbide
epitaxial layer [0066] 11A surface [0067] 100 silicon carbide
epitaxial substrate [0068] 100A surface [0069] 101a, 101b, 101c,
101d measurement area [0070] 110 basal plane dislocation [0071] 400
film deposition apparatus [0072] 401 chamber [0073] 403 induction
heating coil [0074] 404 quartz tube [0075] 405 heat insulator
[0076] 406 heating element [0077] 407 substrate holder [0078] 408
rotatable susceptor
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